Portable analyte monitoring systems, including blood glucometers, are well known in the art. In the case of blood glucometers, these monitors are typically portable meter apparatus that are employed for personal monitoring of blood glucose levels, typically by diabetic patients. Since the 1970's, these devices have gained increasing popularity and acceptance for personal home use in managing when insulin injections are needed by diabetics. These meters have recently become increasingly portable, accurate and convenient due to advances in electronic, optical and test strip chemistry technologies.
The most common type of glucometer used today is based on reflectance optics in conjunction with a disposable, one-use test strip. In use, a small strip carrying reagent chemistry which reacts with blood is employed, such as that described in U.S. Pat. No. 5,296,192, the contents of which are hereby incorporated by reference herein. When fresh whole blood, typically from the lanced finger of a patient, is applied to the test strip, an enzyme-based reaction takes place producing a color change which typically progresses chromatically in proportion to the concentration of glucose present in the blood sample. After blood is applied and the reaction is underway, the strip is then inserted into the monitoring apparatus, and optical reflectance is used to measure the chromatic change. Once the apparatus has determined that the reaction is sufficiently complete, which optimally occurs when the reaction is stabilized, a reflectance measurement is converted through software in the monitoring apparatus into a glucose measurement, typically in mg/DI, and reported on a display to the user.
Such optical monitoring apparatus rely on proper insertion of the strip to ensure alignment of a portion of the strip containing the blood sample and reagent chemistry with the meter optics for accuracy. Further, if the optics become contaminated by blood or other foreign matter, accuracy is also compromised. Because these monitoring apparatus are used by diabetic patients, who frequently suffer sight and motor coordination impairment, it is important that the monitoring apparatus facilitates proper introduction and guided alignment of the strip, as well as protects the optics from contamination. Because of their portability, these apparatus will be subjected to various harsh environments and handling, which could contaminate the optics.
Prior art apparatus are inadequate for addressing these needs. One popular meter, sold under the name ONE TOUCH is described in U.S. Pat. No. 5,843,692. This device requires that the strip be first inserted into the meter and then blood is applied to the strip. This method is inconvenient for the user, as he or she must align a punctured finger with the test site on the strip while it resides in the meter. Consequently, this can result in the inadvertent spillage of blood onto the meter, and subsequently contaminate its optics. Frequently, this will occur when a large blood drop is deposited directly onto the strip. This device also utilizes a door to shield the optics from ambient light during use, which protects the optics when the meter is not in use. Unfortunately, this adds to the testing process the steps of opening and closing the door. Further, because the optical systems of this apparatus requires a door to block ambient light, breakage of the door renders the apparatus unusable.